Radio Shack TRS-80 Model 4 Technical Reference Manual

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(1) F0 FDC Status Reg. FDC Command Reg.
EC - EF Resets RTC Int. Mode Output latch
(2) EB Rcvr Holding Reg. Xmit Holding Reg.
(2) EA UART Status Reg. UART/Modem control
(2) E9 -reserved- Baud Rate Register
(2) E8 Modem Status Master Reset/Enable
UART control reg.
E4 - E7 Read NMI Status Write NMI Mask reg.
E0 - E3 Read INT Status Write INT Mask reg.
(3) CF HD Status HD Command
(3) CE HD Size/Drv/Hd HD Size/Drv/Hd
(3) CD HD Cylinder high HD Cylinder high
(3) CC HD Cylinder low HD Cylinder low
(3) CB HD Sector Number HD Sector Number
(3) CA HD Sector Count HD Sector Count
(3) C9 HD Error Reg. HD Write Precomp.
(3) C8 HD Data Reg. HD Data Reg.
(3) C7 HD CTC channel 3 HD CTC channel 3
(3) C6 HD CTC channel 2 HD CTC channel 2
(3) C5 HD CTC channel 1 HD CTC channel 1
(3) C4 HD CTC channel 0 HD CTC channel 0
(3) C2 - C3 HD Device 10 Reg. - reserved -
(3) C1 HD Control Reg. HD Control Reg.
(3) C0 HD Wr. Prot. Reg. - reserved -
94 - 9F -reserved- -reserved-
(4) 90 - 93 -reserved- Sound Option
(5) 8C - 8F Graphics Sel. 2 Graphics Sel. 2
8B CRTC Data Reg. CRTC Data Reg.
8A CRTC Control Reg. CRTC Control Reg.
89 CRTC Data Reg. CRTC Data Reg.
88 CRTC Control Reg. CRTC Control Reg.
84 - 87 -reserved- Options Register
(5) 83 -reserved- Gra. X Rag. Write
(5) 82 -reserved- Gra. Y Rag. Write
(5) 81 Graphics Ram Rd. Graphics Ram Wr.
(5) 80 -reserved- Gra. Options Reg. Wr
Notes: (1) Valid only if FOC option is installed
(2) Valid only if RS-232 option is installed
(3) Valid only if Hard Disk option is installed
(4) Valid only if sound option is installed
(5) Valid only if High Resolution Graphics option is installed

Radio Shack TRS-80 Model 4 Specifications

General

Brand	Radio Shack
Model	TRS-80 Model 4
Category	Desktop
Language	English